Final answer:
The macrophage theory suggests that cytokine malfunction may be involved in depression, with T-cell imbalances linked to immune profiles in different types of major depressive disorder.
Step-by-step explanation:
The macrophage theory suggests that cytokine malfunction may be involved in depression. Dysregulation of the immune system, particularly through T-cell and cytokine imbalances such as the Th1 and Th2 subtypes, is linked to various immune patterns in major depressive disorder (MDD). Studies indicate increased pro-inflammatory cytokines in MDD, with different immune profiles in melancholic versus non-melancholic depression which can affect response to antidepressant treatment. This information aligns with the macrophage theory's focus on cytokine dysregulation's role in depression.